The present invention relates generally to enclosures and more particularly to underground enclosures.
Underground enclosures are used for a variety of applications, for example, splicing cable, housing slack cable, and housing meters. Enclosures can be made from a variety of materials such as HDPE, polypropylene, concrete, polymer concrete and fiberglass. Polymer concrete enclosures are manufactured using a gravity cast process that utilizes matched surface tooling with a predetermined draft. The draft makes the enclosures smaller on one end versus the other end, which makes the enclosure able to slide out of the mold. Some molds are designed with outside shells that hinge open, but the interior is still manufactured with a core that has a taper. A single piece shell is most desirable as it produces enclosures with the least amount of discontinuities in the reinforcement.
FIGS. 1-3 show a previously available enclosure 10 with exemplary dimensions. Other size and depth enclosures are also available. FIG. 1 shows a cut-away isometric view of enclosure 10. Lid 12 is located in the top opening 14. Bottom opening 16 is located opposite top opening 14. Enclosure 10 includes walls 18 with a foot 20 located at the bottom of walls 18. Foot 20 extends from walls 18 toward bottom opening 16. Walls 18 include a draft angle. FIG. 2 shows a top view of enclosure 10 with exemplary dimensions for top opening 14 and bottom opening 16. Top opening 14 is larger than bottom opening 16 due to the draft of walls 18 and foot 20. FIG. 3 shows a side view of enclosure 10 with wall 18. Enclosure 10 has a depth of 24″.
Users of enclosures may need a deeper enclosed space than the depth on a specific enclosure. To achieve the required enclosed space, users may stack multiple enclosures on top of one another to achieve the desired depth. This can be accomplished by some previously available enclosures, but the users are limited by the draft angle required to remove the enclosures from a mold during the manufacturing processes of the enclosures. As discussed, the draft angle makes the enclosures smaller on one end versus the other end, which results in the inability to stack enclosures if the smaller end (bottom) of the top enclosure is smaller than the opening of the bottom enclosure. If the smaller end (bottom) of the top enclosure is smaller than the opening of the bottom enclosure, the top enclosure will fall through the opening in the bottom enclosure. Deeper enclosures have a greater difference in the sizes of the top and bottom ends due to the influence of the draft angle. Accordingly, only certain enclosure depths can be stacked on top of one another.